I was recently at a range and the guy next to me was shooting a "limited edition cowboy action" rifle. He said it was the the octagonal barrel that made it unique. So my question: is there a benefit to that kind of barrel, and back in the days of the cowboy, how were they able to make that barrel?

might be limited edition now but back in the day all rifles were made that way. You can see once you get towards the end of the 19th century that the machining equipment started to get better and you started seeing half rounds and round barrels.

The original way of making barrels was to wrap strips of iron around a mandrel in spiral fashion, sometimes twisting the straps in doing so. this spiral wound tube wass then welded into a solid iron tube (Damascus barrel). This rough tube was then filed into hexagon shape. It remained the mark of quality. And, the hexagon shape added weight out front, in a muzzle-heavy rifle that held steady for off-hand shooting.

As the use of lathes came into use, round, or tapered barrels came into vogue. The lighter weight was appreciated by the horse soldier and horse.